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The metastasis suppressor Nm23 as a modulator of Ras/ERK signaling
1Department of Biological Anthropology, Eötvös Loránd University, Pázmány Péter stny. 1/C, H-1117 Budapest, Hungary.
Abstract:
NM23-H1 (also known as NME1) was the first identified metastasis suppressor, which displays a nucleoside diphosphate kinase (NDPK) and histidine protein kinase activity. NDPKs are linked to many processes, such as cell migration, proliferation, differentiation, but the exact mechanism whereby NM23-H1 inhibits the metastatic potential of cancer cells remains elusive. However, some recent data suggest that NM23-H1 may exert its anti-metastatic effect by blocking Ras/ERK signaling. In mammalian cell lines NDPK-mediated attenuation of Ras/ERK signaling occurs through phosphorylation (thus inactivation) of KSR (kinase suppressor of Ras) scaffolds. In this review I summarize our knowledge about KSR's function and its regulation in mammals and in C. elegans. Genetic studies in the nematode contributed substantially to our understanding of the function and regulation of the Ras pathway (i.e. KSR's discovery is also linked to the nematode). Components of the RTK/Ras/ERK pathway seem to be highly conserved between mammals and worms. NDK-1, the worm homolog of NM23-H1 affects Ras/MAPK signaling at the level of KSRs, and a functional interaction between NDK-1/NDPK and KSRs was first demonstrated in the worm in vivo. However, NDK-1 is a factor, which is necessary for proper MAPK activation, thus it activates rather than suppresses Ras/MAPK signaling in the worm. The contradiction between results in mammalian cell lines and in the worm regarding NDPKs' effect exerted on the outcome of Ras signaling might be resolved, if we better understand the function, structure and regulation of KSR scaffolds.
Insights
NM23-H1, a metastasis suppressor, may inhibit cancer spread by blocking Ras/ERK signaling. Its regulation of KSR scaffolds differs between mammals and worms, requiring further study to resolve contradictions.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- NM23-H1 (NME1) is the first identified metastasis suppressor with nucleoside diphosphate kinase (NDPK) and histidine protein kinase activity.
- NDPKs influence cell migration, proliferation, and differentiation, but NM23-H1's anti-metastatic mechanism is unclear.
- Recent evidence suggests NM23-H1 inhibits metastasis by blocking Ras/ERK signaling, potentially via KSR scaffold inactivation in mammals.
Purpose of the Study:
- To review the function and regulation of kinase suppressor of Ras (KSR) scaffolds in mammals and C. elegans.
- To explore the role of NM23-H1 (NME1) and its worm homolog NDK-1 in Ras/MAPK signaling.
- To reconcile conflicting data on NDPK effects on Ras signaling between mammalian and nematode systems.
Main Methods:
- Literature review focusing on KSR function, regulation, and interaction with NDPKs.
- Comparative analysis of Ras/MAPK pathway components and NDPK homologs in mammals and C. elegans.
- Examination of genetic studies in C. elegans contributing to Ras pathway understanding.
Main Results:
- KSR scaffolds and Ras/ERK pathway components are conserved between mammals and C. elegans.
- Worm NDK-1 interacts with KSRs and is necessary for MAPK activation, suggesting a contrasting role to mammalian NM23-H1.
- Mammalian NM23-H1 may inactivate KSR, while worm NDK-1 appears to activate Ras/MAPK signaling.
Conclusions:
- Understanding KSR scaffold function, structure, and regulation is crucial for resolving the contradictory roles of NDPKs in Ras signaling.
- The conserved RTK/Ras/ERK pathway offers a model for studying metastasis suppression.
- Further research is needed to elucidate the precise mechanisms of NM23-H1 and NDK-1 in regulating Ras/MAPK signaling and their impact on cancer metastasis.
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